import thousands of products, what plug in?

What is the best, free or cheapest way to import 1000's of products, images and cvs files?

NopCommerce does have import features. You can import around 500-1000 products at once using the import feature of NopCommerce which is available at the product listing page in the admin section.

I may have 30,000

You can create a new scheduled task and use it to run the import. You can break the listing to 5-10 excel files, upload those in some directory in the server and let the schedule task pick and process the files one after another(make sure you don not reprocess the processed file) so that you do not have to wait and process the files manually. I am not sure whether it is the most effective idea but it should get the job done.

i'll try soon, thank you

I exported from nopcommerce, added some items in excel and now get this message.
The file is not an valid Package file. If the file is encrypted, please supply the password in the constructor.

I managed to do it from a new version of excel, but can I leave some cells blank?

Yes, it's not mandatory to have all cells filled. Be sure you provide product name, price, and SKU if available.

All Images just stay on my server in a folder for the nopcommerce site to point to I guess also?